Update CI linter

.github/config/checks.xml

@@ -28,7 +28,18 @@
     <module name="Translation" />
 
     <!-- Checks for size violations -->
-    <module name="FileLength" />
+    <!-- Error-level FileLength (for src files) -->
+    <module name="FileLength">
+        <property name="id" value="FileLengthError"/>
+        <property name="max" value="2000"/>
+        <property name="severity" value="error"/>
+    </module>
+    <!-- Warning-level FileLength (for test files) -->
+    <module name="FileLength">
+        <property name="id" value="FileLengthWarn"/>
+        <property name="max" value="2000"/>
+        <property name="severity" value="warning"/>
+    </module>
     <module name="LineLength">
         <property name="id" value="LineLength"/>
         <property name="fileExtensions" value="java" />
@@ -183,7 +194,11 @@
         <!-- Miscellaneous other checks -->
         <module name="ArrayTypeStyle" />
         <module name="CommentsIndentation" />
-        <module name="TodoComment" />
         <module name="UpperEll" />
+
+        <!-- TODO comments raise warnings but don't throw errors -->
+        <module name="TodoComment">
+            <property name="severity" value="warning" />
+        </module>
     </module>
 </module>

.github/config/suppressions.xml

@@ -10,6 +10,7 @@
 
     <!-- Checks for size violations -->
     <suppress checks="LineLength" files="test/*" id="LineLength" />
+    <suppress checks="LineLengthTest" files="src/*" id="LineLength" />
 
     <!-- Checks for Javadoc comments -->
     <suppress checks="JavadocVariable" files="test/*" />
@@ -21,4 +22,14 @@
 
     <!-- Checks for class design-->
     <suppress checks="VisibilityModifier" files="/sim/*" />
+
+
+    <!-- Checks for filelengths -->
+    <suppress checks="FileLength"
+              id="FileLengthError"
+              files="test/*" />
+    <!-- Suppress warning-level FileLength in non-test files -->
+    <suppress checks="FileLength"
+              id="FileLengthWarn"
+              files="src/*" />
 </suppressions>

.github/workflows/lint.yml

@@ -15,12 +15,12 @@ jobs:
         fetch-depth: 0
 
     - name: Lint code base
-      uses: dbelyaev/action-checkstyle@v0.9.5
+      uses: dbelyaev/action-checkstyle@v3.0.0
       with:
         github_token: ${{ secrets.GITHUB_TOKEN }}
         reporter: github-check
         checkstyle_config: .github/config/checks.xml
-        fail_on_error: true
+        fail_level: error
 
   update-lint-badges:
     if: ${{ always() && github.ref == 'refs/heads/main' }}

src/arcade/core/gui/GUI.java

@@ -371,7 +371,7 @@ public File getPath() {
     }
 
     /** Custom file filter for XML files. */
-    private static class XMLFileFilter extends FileFilter {
+    private static final class XMLFileFilter extends FileFilter {
         /**
          * Determines if the file is an XML file.
          *